LONDON, UK–( EMWNews – April 8, 2008) –

London, UK, 8 April 2008 – Cancer drug developer Antisoma plc (LSE: ASM; USOTC:ATSMY) today announces the publication of data on the

selective killing of breast cancer cells by Antisoma’s

nucleolin-targeting aptamer AS1411. The work was carried out by

Professor Daniel Fernandes and colleagues at the Medical University

of South Carolina (MUSC) and is published in the April issue of the

journal Cancer Research.

Professor Fernandes and his team compared the effects of AS1411 on a

breast cancer cell line and on a normal breast cell line. A 5 umol/l

dose clearly inhibited the growth of breast cancer cells. In

contrast, a four-fold higher dose had no discernible effect on normal

breast cells. The selective action of AS1411 on cancer cells

correlated with two differences between cancer cells and normal

cells. First, cancer cells expressed considerably more nucleolin in

their cytoplasm. Second, cancer cells internalised more AS1411.

The authors investigated how AS1411 kills breast cancer cells once it

is internalised. They showed that the drug down-regulates the

messenger RNA encoding Bcl-2, a protein that allows cancer cells to

avoid death by apoptosis. Previous work from Professor Fernandes’

group has shown that nucleolin plays an important role in maintaining

Bcl-2 levels in certain cancer cells. It does this by binding to and

stabilising Bcl-2 messenger RNA. AS1411 acts as a ‘molecular decoy,’

binding nucleolin and preventing its interaction with Bcl-2 messenger

RNA. This leads to a fall in Bcl-2 messenger RNA levels, a consequent

fall in the level of the Bcl-2 protein and, ultimately, apoptosis.

Professor Fernandes said: “We continue to gain new insights into how

AS1411 acts though nucleolin to induce the death of tumour cells.

Ability to avoid apoptosis is a fundamental property of cancer cells,

and so the discovery that AS1411 interferes with the Bcl-2 pathway

that protects cancer cells from apoptosis is an exciting

observation.”

Dr Ursula Ney, Antisoma’s Chief Operating Officer, added: “These

encouraging findings suggest that AS1411 could have potential in

breast cancer, which is among the most common cancers worldwide.”

AS1411 is currently in a randomised phase II study in acute myeloid

leukaemia, with further phase II studies planned in renal and other

cancers.

Enquiries:

Glyn Edwards, CEO

Daniel Elger, Director of Communications        +44 (0)7909 915 068

Antisoma plc



Mark Court/Lisa Baderoon/Rebecca Skye Dietrich  +44 (0)20 7466 5000

Buchanan Communications



Brian Korb                                      +1 646 378 2923

The Trout Group

Except for the historical information presented, certain matters

discussed in this statement are forward looking statements that are

subject to a number of risks and uncertainties that could cause

actual results to differ materially from results, performance or

achievements expressed or implied by such statements. These risks and

uncertainties may be associated with product discovery and

development, including statements regarding the company’s clinical

development programmes, the expected timing of clinical trials and

regulatory filings. Such statements are based on management’s current

expectations, but actual results may differ materially.

Notes for Editors:

Background on AS1411

Aptamers are short pieces of DNA or RNA that can fold into stable,

three-dimensional structures capable of interacting with particular

target proteins. AS1411 is the first aptamer to be tested as a

treatment for cancer. It binds to the protein nucleolin, which is

found on the surface of cancer cells. It is then internalised and has

been shown to kill cancer cells from a variety of cell lines. The

drug has also shown anti-cancer effects in animal models and

promising signs of anti-cancer activity in the clinic. AS1411 was

originally developed by Dr Paula Bates, Dr John Trent and Prof.

Donald Miller at the University of Alabama and then at the University

of Louisville. Antisoma added AS1411 to its pipeline when it acquired

the Louisville-based company Aptamera Inc. in February 2005.

Background on Antisoma

Headquartered in London, UK, Antisoma is a biopharmaceutical company

that develops novel products for the treatment of cancer. Antisoma

fills its development pipeline by acquiring promising new product

candidates from internationally recognised academic or cancer

research institutions. Its core activity is the preclinical and

clinical development of these drug candidates. Please visit

www.antisoma.com for further information about Antisoma.

—END OF MESSAGE—

Copyright © Hugin AS 2008. All rights reserved.